This invention pertains to the art of pumps and more particularly to electrically driven pumps capable for use as heart pumps.
The invention is applicable to a pump device for the pumping of blood of a living person, or of a living animal, to replace or assist the pumping function of a heart. The pump is intended for intrathoracic disposition and is further capable of being sized for a fit inside the pumping chamber of a human heart. However, it will be appreciated to those skilled in the art that the invention could be readily adapted for use in other environments as, for example, where a particularly durable pump is desired which is compact in size, which does not use a shaft seal, and which avoids injury or destruction of the pumped material.
Conventional continuous flow heart assist devices have suffered from a predominant problem, the lack of relative durability due to the use of a shaft seal. Because of their intended implantation in a living being, a long life span for the pump device is a primary design objective. However, the working environment for the pump, i.e., the pumping of blood, imposes severe design conditions which have not previously been satisfactorily overcome. Most commercially available blood pumps employ a motor encased in a housing where the motor is operating in an air or saline environment. The shaft of the motor will typically extend through a sealed wall of the housing into a blood chamber to drive an impeller to urge the blood through the pump. The most common cause of failure of such prior known pumps is the failure or leakage of the seal about the shaft which either causes blood leaking into the drive compartment, or worse, saline or air leaking into the blood stream. In addition, the high shear and frictional heating occurring at the shaft-to-seal interface is prone to injure the blood and/or cause clotting.
Another problem that has occurred with prior heart pumps is stagnant blood in areas of the pump which lack sufficient wash flow. Stagnant blood will also have a tendency to clot.
Various forms of blood pumps have heretofore been suggested to overcome the problems of blood pump shaft seals. It has been found that the defects present in these prior pump devices are such that the devices are of limited economic and practical value.
In particular, it has been suggested to suspend the impeller magnetically in three dimensions to avoid the penetrating shaft into the blood chamber. However, the problems of maintaining an appropriate magnetic suspension of a rotating impeller have shown that a commercially feasible blood pump with this design is technically impractical at the present time.
Alternatively, some prior magnetically driven impellers that lack the shaft seal have not been able to overcome problems of damage to the pumped blood due to stagnant blood in some areas or have caused problems with damage to the blood at bearings which support the impeller.
The present invention contemplates a new and improved device which overcomes all of the above referred to problems and others to provide a new blood pump or pump assist device which is simple in design having only a single moving part, economical to manufacture, readily adaptable to a plurality of dimensional characteristics, sealless between the impeller and the motor, and which provides improved blood pumping.